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Many migratory birds exhibit interannual consistency in migration schedules, routes and stopover sites. Detecting the interannual consistency in spatiotemporal characteristics helps understand the maintenance of migration and enables the implementation of targeted conservation measures. We tracked the migration of Whimbrel (Numenius phaeopus) in the East Asian–Australasian Flyway and collected spatiotemporal data from individuals that were tracked for at least two years. Wilcoxon non-parametric tests were used to compare the interannual variations in the dates of departure from and arrival at breeding/nonbreeding sites, and the interannual variation in the longitudes when the same individual across the same latitudes. Whimbrels exhibited a high degree of consistency in the use of breeding, nonbreeding, and stopover sites between years. The variation of arrival dates at nonbreeding sites was significantly larger than that of the departure dates from nonbreeding and breeding sites. Repeatedly used stopover sites by the same individuals in multiple years were concentrated in the Yellow Sea coast during northward migration, but were more widespread during southward migration. The stopover duration at repeatedly used sites was significantly longer than that at sites used only once. When flying across the Yellow Sea, Whimbrels breeding in Sakha (Yakutia) exhibited the highest consistency in migration routes in both autumn and spring. Moreover, the consistency in migration routes of Yakutia breeding birds was generally higher than that of birds breeding in Chukotka. Our results suggest that the northward migration schedule of the Whimbrels is mainly controlled by endogenous factors, while the southward migration schedule is less affected by endogenous factors. The repeated use of stopover sites in the Yellow Sea coast suggests this region is important for the migration of Whimbrel, and thus has high conservation value.

Reproduction investment is a prominent trade-off in life-history theory and is subject to strong selection pressure. The avian eggshell, as a crucial barrier between the bird embryo and the surrounding environment, undergoes optimization under different environmental selection regimes to ensure the successful development of embryos, which can be linked to local adaptation. Therefore, understanding the variation in eggshell microstructure and composition in wild bird populations living in contrasting ambient environments is of great significance. In this study, we utilized electron microscope ultrastructure measurement and elemental analyses to measure and compare the microstructure and element composition of eggshells from three wild plover populations (Charadrius alexandrinus and C. dealbatus) residing in heterogeneous habitats across varied climatic zones. These populations include the high-altitude Qinghai Lake population, the temperate coastal Tangshan population, and the tropical coastal Zhanjiang population. Our findings revealed that the palisade layer was thinner in the Qinghai Lake population compared to its lowland populations. This difference might be attributed to hypoxia which facilitates the hatching process by allowing chicks to easily break through their shells. Additionally, the variations in the elemental composition of the eggshells among populations well reflected the distribution of element content in different geographical regions. The Qinghai Lake population displayed low zinc and low manganese levels but high calcium levels, while the Zhanjiang population exhibited high zinc, high iron, high manganese, and high phosphorus levels. Furthermore, these variations in elemental composition could also account for the observed microstructural differences among populations. Collectively, we propose that the dissimilarities in eggshell microstructure and elemental composition among populations could be attributed to adaptations to different environmental conditions. Our findings lay the groundwork for future research to explore the mechanisms behind the variations in eggshell characteristics among wild bird populations, and contribute to a broader understanding of biodiversity mechanisms.

China's coastal wetlands provide breeding, migration stopover, and wintering habitats for about 230 waterbird species, which is more than a quarter of all waterbirds in the world. Large-scale and high intensity human activities have resulted in serious loss and degradation of coastal wetlands over the past half century, causing population declines in many waterbirds. Through a literature review and expert surveys, this article reviews conservation measures taken in recent decades to protect waterbirds in China's coastal wetlands and provides recommendations for future conservation action from three aspects: policy and administration, habitat conservation and management, and multiparty participation. Over the past decades, many conservation legislation, regulations and action plans at the national level and more site-specific measures and interventions have been implemented, with notable improvement in the effectiveness in policy making and multi-stakeholder participation. Accordingly, some threats to waterbirds have been mitigated and many key sites for waterbirds have been designated as strictly protected nature reserves. However, some critical issues still remain, mostly related to habitat conservation and management, such as coastal wetland restoration, control of invasive Spartina alterniflora, control of environmental pollution, and improvement of artificial habitat quality. We highlight that protecting natural tidal wetlands and improving habitat quality are critical for the conservation of coastal waterbirds, especially those highly dependent on the intertidal wetlands. China has demonstrated strong commitment to ecological conservation and restoration for the future, in terms of both funding and policies for biodiversity and wetland ecosystems. It is important that this commitment to conserve coastal waterbirds is supported continuously by science- and evidence-based decisions and actions.

Abstract Background Despite an increasing number of surveys and a growing interest in birdwatching, the population and distribution of Asian Dowitcher (Limnodromus semipalmatus), a species endemic to the East Asian–Australasian and Central Asian Flyways, remains poorly understood, and published information about the species is largely outdated. In boreal spring 2019, over 22,432 Asian Dowitchers were recorded in a coastal wetland at Lianyungang, Jiangsu Province, China, constituting 97.5% of its estimated global population. Methods In 2019 and 2020, we conducted field surveys at Lianyungang to determine the numbers of Asian Dowitchers using the area during both southward and northward migrations. We also assessed the distribution and abundance of Asian Dowitchers elsewhere along the China coast by searching literature and consulting expert opinion. Results The coastal wetlands of Lianyungang are the most important stopover site for Asian Dowitchers during both northward and southward migrations; they supported over 90% of the estimated global population during northward migration in two consecutive years (May 2019 and 2020). This area also supported at least 15.83% and 28.42% (or 30.74% and 53.51% using modelled estimates) of the global population during southward migration in 2019 and 2020 respectively. Coastal wetlands in the west and north of Bohai Bay also have been important stopover sites for the species since the 1990s. Although comprehensive, long-term monitoring data are lacking, available evidence suggests that the population of the species may have declined. Conclusions The high concentration of Asian Dowitchers at Lianyungang during migration means the species is highly susceptible to human disturbances and natural stochastic events. The coastal wetlands of Lianyungang should be protected and potentially qualify for inclusion in China’s forthcoming nomination for World Heritage listing of Migratory Bird Sanctuaries along the Coast of Yellow Sea-Bohai Gulf of China (Phase II) in 2023. Additional research is needed to understand Asian Dowitchers’ distribution and ecology, as well as why such a high proportion of their population rely on the Lianyungang coast.

Background: Despite an increasing number of surveys and a growing interest in birdwatching, the population and distribution of Asian Dowitcher (Limnodromus semipalmatus), a species endemic to the East Asian–Australasian and Central Asian Flyways, remains poorly understood, and published information about the species is largely outdated. In boreal spring 2019, over 22,432 Asian Dowitchers were recorded in a coastal wetland at Lianyungang, Jiangsu Province, China, constituting 97.5% of its estimated global population. Methods: In 2019 and 2020, we conducted field surveys at Lianyungang to determine the numbers of Asian Dowitchers using the area during both southward and northward migrations. We also assessed the distribution and abundance of Asian Dowitchers elsewhere along the China coast by searching literature and consulting expert opinion. Results: The coastal wetlands of Lianyungang are the most important stopover site for Asian Dowitchers during both northward and southward migrations; they supported over 90% of the estimated global population during northward migration in two consecutive years (May 2019 and 2020). This area also supported at least 15.83% and 28.42% (or 30.74% and 53.51% using modelled estimates) of the global population during southward migration in 2019 and 2020 respectively. Coastal wetlands in the west and north of Bohai Bay also have been important stopover sites for the species since the 1990s. Although comprehensive, long-term monitoring data are lacking, available evidence suggests that the population of the species may have declined. Conclusions: The high concentration of Asian Dowitchers at Lianyungang during migration means the species is highly susceptible to human disturbances and natural stochastic events. The coastal wetlands of Lianyungang should be protected and potentially qualify for inclusion in China's forthcoming nomination for World Heritage listing of Migratory Bird Sanctuaries along the Coast of Yellow Sea-Bohai Gulf of China (Phase II) in 2023. Additional research is needed to understand Asian Dowitchers' distribution and ecology, as well as why such a high proportion of their population rely on the Lianyungang coast. [ABSTRACT FROM AUTHOR]

Abstract Background Anthropogenic disturbance can negatively affect an animal’s energy budget by evoking movement responses. Existing research focuses mainly on immediate displacement as a disturbance effect, since this can be easily observed in the field. However, effects on movement over longer timescales are poorly examined and it is largely unknown if and to what extent they reflect immediate responses. Longer-term responses could for example be larger than immediate responses if birds, after disturbance, return to the original location and thereby travel twice the immediate disturbed distance. Methods We combined GPS tracking data with observational data to quantify the effects of anthropogenic (air force and walkers) and non-anthropogenic disturbances on distances travelled by roosting Eurasian Oystercatchers (Haematopus ostralegus) during the non-breeding season. We compared immediate displacement after a disturbance with distance travelled during the entire high tide period (longer-term response), while accounting for environmental factors. Additionally, we calculated energy expenditure due to disturbance based on observed disturbance frequencies. Results Disturbance resulted in an immediate displacement response of ~ 200 m (median). Air force disturbances tended to yield larger immediate responses than walker and, especially, than non-anthropogenic disturbances. Longer-term responses and immediate responses were approximately similar, suggesting that, over longer timescales, spatial disturbance effects in the study area remain confined to immediate effects. However, disturbances were infrequent (0.17 disturbances per bird per hour) and most disturbances were of natural origin (62%). Consequently, anthropogenic disturbance of roosting oystercatchers in the study area on average costs 0.08% of the daily energy expenditure. Conclusions Our results suggest that immediate spatial responses to disturbance can be a useful proxy for spatial responses over longer timescales. Over the non-exhaustive range of conditions investigated, energetic consequences of spatial disturbance responses for an oystercatcher in the study area are marginal due to low disturbance levels.

Abstract Background Restoration projects have been implemented worldwide to mitigate the adverse effects of the loss and degradation of wetland habitats. Much research has been carried out on the impacts on birds of wetland restoration and management projects in China. Studies have mainly investigated central or coastal wetlands, while inland wetlands in remote areas have been much less studied. We focused on examining the response of wild birds to wetland restoration in Dianchi Lake, south-west China. Methods The line transect method was performed at 26 sampling plots. Three of these were in the city, and to acquire all wild bird data 23 plots were located every 2–8 km along the shore of Dianchi Lake, between December 2011 and November 2013. We collected all related bird records by searching the available literature, articles, newspapers and records of birdwatchers to compare species variation before and after implementation of wetland restoration. To measure the relationships between waterbird assemblages and habitat structures, we used canonical correspondence analysis (CCA) to pair the main matrix of bird assemblages with a second matrix of habitat variables. Results We recorded 182 bird species belonging to 51 families and 17 orders. Of the species, 42 were new records for Kunming City and 20 were new records for Yunnan Province. Ten waterbird species were found to have disappeared from the shore of Dianchi Lake. CCA results indicated that waterbirds could be divided into four categories based on their habitat preference: synanthropic (wintering gulls), special habitat (shorebirds), semi-natural (wintering coots and ducks) and disturbance-tolerant (resident) species. Conclusions Our study is the first to consider the entire wild bird community throughout the year and discuss the species variation before and after wetland restoration projects launched for Dianchi Lake. Distinct habitat requirements of different waterbird groups were detected in our study, suggesting different types of restoration and management should be implemented.

Abstract Background Departure decisions and behaviors of migratory birds at stopover sites are expected to maximize fitness by trade-offs among avoiding predators, optimizing refueling (energy) capacity, and matching other life-history events. We predict that species with different body sizes and migratory destinations will exhibit different behaviors when departing from the same stopover site. We also predict that with strong time constraint at the final pre-breeding stopover site, departure decisions may be less sensitive to exogenous factors, such as wind condition, compared to other stopover or nonbreeding sites. Methods We recorded migratory departures of four shorebird species, i.e. Eurasian Curlew (Numenius arquata), Bar-tailed Godwit (Limosa lapponica), Great Knot (Calidris tenuirostris), and Grey Plover (Pluvialis squatarola), at Yalujiang Estuary Wetlands in China, a final pre-breeding stopover site in the northern Yellow Sea, from 2011 to 2014. We compared flock sizes, departure time and departure directions between species, and investigated the effects of tide and weather conditions (rain and ground wind speed and direction) on the departure decision of shorebirds. Results We found that larger species departed in smaller flocks and were more variable in daily departure time. Departure trajectory of all four species appeared to be influenced by coastal topography. With the east–west coastline and intertidal mudflat on the south, birds exhibited westward or eastward deflection from the shortest migratory routes. Bar-tailed Godwit was the only species that deviated to the southeast and did not climb over the land. Birds avoided departure during precipitation, while their departure was not related to ground wind benefit or tidal condition. Conclusions Body size among species, which influences their vulnerability to predators, might be important in shaping shorebird departure strategies. Diverse departure directions could be the result of different wind use tactics in climbing stage. Narrow optimal time window of breeding might lead to reduced flexibility in departure date at a final pre-breeding site. Both endogenous and exogenous are important in shaping departure behaviors and decisions.

Reproduction investment is a prominent trade-off in life-history theory and is subject to strong selection pressure. The avian eggshell, as a crucial barrier between the bird embryo and the surrounding environment, undergoes optimization under different environmental selection regimes to ensure the successful development of embryos, which can be linked to local adaptation. Therefore, understanding the variation in eggshell microstructure and composition in wild bird populations living in contrasting ambient environments is of great significance. In this study, we utilized electron microscope ultrastructure measurement and elemental analyses to measure and compare the microstructure and element composition of eggshells from three wild plover populations (Charadrius alexandrinus and C. dealbatus) residing in heterogeneous habitats across varied climatic zones. These populations include the high-altitude Qinghai Lake population, the temperate coastal Tangshan population, and the tropical coastal Zhanjiang population. Our findings revealed that the palisade layer was thinner in the Qinghai Lake population compared to its lowland populations. This difference might be attributed to hypoxia which facilitates the hatching process by allowing chicks to easily break through their shells. Additionally, the variations in the elemental composition of the eggshells among populations well reflected the distribution of element content in different geographical regions. The Qinghai Lake population displayed low zinc and low manganese levels but high calcium levels, while the Zhanjiang population exhibited high zinc, high iron, high manganese, and high phosphorus levels. Furthermore, these variations in elemental composition could also account for the observed microstructural differences among populations. Collectively, we propose that the dissimilarities in eggshell microstructure and elemental composition among populations could be attributed to adaptations to different environmental conditions. Our findings lay the groundwork for future research to explore the mechanisms behind the variations in eggshell characteristics among wild bird populations, and contribute to a broader understanding of biodiversity mechanisms. [ABSTRACT FROM AUTHOR]

China's coastal wetlands provide breeding, migration stopover, and wintering habitats for about 230 waterbird species, which is more than a quarter of all waterbirds in the world. Large-scale and high intensity human activities have resulted in serious loss and degradation of coastal wetlands over the past half century, causing population declines in many waterbirds. Through a literature review and expert surveys, this article reviews conservation measures taken in recent decades to protect waterbirds in China's coastal wetlands and provides recommendations for future conservation action from three aspects: policy and administration, habitat conservation and management, and multiparty participation. Over the past decades, many conservation legislation, regulations and action plans at the national level and more site-specific measures and interventions have been implemented, with notable improvement in the effectiveness in policy making and multi-stakeholder participation. Accordingly, some threats to waterbirds have been mitigated and many key sites for waterbirds have been designated as strictly protected nature reserves. However, some critical issues still remain, mostly related to habitat conservation and management, such as coastal wetland restoration, control of invasive Spartina alterniflora , control of environmental pollution, and improvement of artificial habitat quality. We highlight that protecting natural tidal wetlands and improving habitat quality are critical for the conservation of coastal waterbirds, especially those highly dependent on the intertidal wetlands. China has demonstrated strong commitment to ecological conservation and restoration for the future, in terms of both funding and policies for biodiversity and wetland ecosystems. It is important that this commitment to conserve coastal waterbirds is supported continuously by science- and evidence-based decisions and actions. [ABSTRACT FROM AUTHOR]